Common examples of roadside posts include sign posts and guide posts, which are usually located on the edge or shoulder of roadways to delineate lanes and direct traffic. Guide posts are particularly effective when visibility is impaired, such as at night on unlit highways. Retro-flective sheeting is commonly used on delineator guide posts in various grades to reflect light and indicate to motor vehicle drivers the varying contours and directions of the approaching section of road.
Roadside posts are often impacted and damaged by wayward vehicles and must be replaced or repaired. Timber posts will commonly fracture when impacted and must be replaced. Existing plastic or plastic/rubber composite posts are flexible and resilient enabling them to recover after impact. However, plastic or rubber posts tend to deteriorate due to UV exposure and repeated impacts over time. Steel posts have also been employed and are generally not resilient, plastically deforming upon impact and must be manually restraightened. Some known devices also employ a hinging mechanism between two or more rigid members. The hinging mechanism is typically a flexibly resilient rubber or plastic material. The rubber or plastic components of these posts also deteriorate due to UV exposure and repeated impacts. Other hinging mechanisms are either not resilient or complicated and expensive to manufacture.
Often the nature of the vehicle impact is a direct wheel-over in which the vehicle wheel rolls directly over the post pressing it flat against the surface of the ground. Known posts are installed in the ground to bend only above the surface of the ground and are therefore, not adapted to bend flat against the ground surface without enduring a tight right angle bend at the surface. During a direct wheel-over, flexible posts are forced to bend substantially at a tight right angle at the ground surface. Subsequently, during a direct wheel-over, crease points can occur in the post at the surface of the ground as the post is forced into a tight right angle bend. Tight right angle bends accelerate fatigue of the post and also increase plastic deformation in metal posts.